Performance of elite and heritage germplasm in barley genotype mixtures: effects on yield and disease under diverse management scenarios

Genotype mixtures are multiple crop lines grown together to improve yield, stability, and disease control by utilizing different genetic and morphological traits. Incorporating heritage germplasm may enable exploitation of low input adaptation traits while retaining the high yield of elite modern cultivars. However, the effects of nutrient application, sowing density, and disease management on competition/facilitation dynamics in genotype mixtures with diverse germplasms, such as landraces, remain largely unknown. A set of complimentary plot experiments, undertaken in the arable cropping area of the east of Scotland, assessed genotype mixtures using heritage lines and/or elite cultivars of both spring and winter barley. The experimental systems manipulated the sowing densities, mixture composition, nitrogen application, and fungal disease pressure across three different field seasons. Here we show that the advantages of genotype mixtures were highly dependent on the genotypic makeup of the mixture and the environmental conditions in which they are grown, demonstrating complex genotype mixture × environment interactions. Genotype mixture performance in barley is highly dependent on the interaction of genetic composition and management factors. This paper revealed, for the first time, that small amounts of heritage germplasm enhanced yield stability, though overall yields rarely match those of the elite monocultures and no consistent disease reduction was observed. Although barley gains limited benefits from mixing genotypes, our study is able to highlight complex trends in mixture composition and environment that are relevant for crops with greater genotype mixture yield benefits.